Regulating device for centrifugal separators



Sept. 4, 1962 H. w. THYLEFORS 3,052,401

REGULATING DEVICE FOR CENTRIFUGAL SEPARATORS Filed Dec. 23, 1958 IN VEN TOR.

ATTORN Eys This invention relates to centrifugal separators and particularly to an improved device for regulating the flow to and from a centrifugal separator.

In certain centrifugal separators, the outlet is provided with a paring means in direct communication with a discharge pipe line or this pipe line is connected to a pump arranged in the outlet from the separator bowl. In such separators, the pressure energy or velocity energy of the separated liquid leaving the separator may be utilized for the transport of the liquid through the pipe line to the de sired point of delivery. In such cases, it is often desirable to provide for regulation of the liquid flow in the pipe line at a point of the line which is more or less remote from the separator proper. This is desired, for instance, in air-craft carriers where separators for purification of the areo-motor fuel are installed below deck and are connected through lines with tapping places on the deck. With such an arrangement, special measures must be taken to prevent an overflow in the separator when shutting off the discharge line.

Also, in centrifugal separators of the well known type provided with a liquid seal, the latter under unfavorable conditions may be destroyed, with the result that the material to be separated discharges over the overflow outlet for the liquid in the liquid seal.

In centrifugal separators of the so-called purifier type, the position of the boundary surface between the separation components in the centrifugal bowl is of the utmost importance for the desired separation result. The boundary surface may easily be displaced in one direction or the other by changing the pressure in the outlets. Here, however, a problem appears in that it is difficult to attain the best position for the boundary surface owing to the ditficulty of determining when the boundary surface is in this position.

The present invention has for its principal object the provision of a centrifugal separator having a regulating device which overcomes the above-noted problems.

A separator made according to the invention has a return line by which the feed line to the centrifugal bowl is connected to a discharge line leading fom the bowl. In this return line is a shut-off device which preferably is spring-loaded. This shut-off device is movable and has a first extreme position for closing the feed line while the return line is open, and opposite extreme position for closing both the feed line and the return line, and an intermediate position for closing the return line while the feed line is open. The separator also has means for moving the shut-off device in response to variations in the difference between the pressures in the feed and discharge lines.

A preferred form of the invention is described in greater detail below, reference being made to the accompanying drawings in which:

FIG. 1 is a schematic view of a centrifugal separator embodying the new regulating device;

FIG. 2 is a vertical sectional View of the centrifugal bowl of the separator, and

FIG. 3 is a longitudinal sectional View of the regulating device proper.

In FIG. 1, reference numeral 1 designates a centrifugal separator having a feed line 2 and a discharge line 3.

In the discharge line 3 is a shut-01f valve 4. The feed and discharge lines both pass through a regulating device 5. The outlet of the centrifuge 1 is provided with a paring means or a discharge pump. With respect to its inlet, the centrifuge may be of the hermetic type or totally open. A centrifuge bowl 6 in which the inlet is open and the outlet has a paring means, is shown in FIG. 2. The paring means as there shown comprises a con ventional paring disc 7 connected to a discharge tube 3a. A feed tube 2a opens into a distributing chamber 8 from which the material to be separated is led in the usual manner through distributing channels 9 into the separation chamber. The latter contains bowl discs 10 and a top disc 11 which extends outside the bowl discs 10 and together with the heavier liquid component forms a liquid seal from which excess liquid discharges through an outlet 12. The separated lighter liquid component passes between the top disc 11 and the distributor 13 to the chamber in which the stationary paring disc- 7 is arranged, the liquid being picked up by the parer 7 in the well known manner and discharged through tub 3a, regulator 5 and pipe 3.

The regulating device 5, which is shown in detail in FIG. 3, is provided with two connecting flanges 14, 15 by which the pipes 2 and 3, respectively, in FIG. 1 are connected to two throughflow passages 15, 17, respectively. These passages at their inner ends lead to pipe fittings 18 and 19, respectively, which are connected in any suitable maner to the feed tube 2a and discharge tube 3a, respectively, in FIG. 2.

Between the passages 16 and 17 is a communication channel or return line 20 which can be closed by means of a slide or piston 21. The latter is connected through a valve spindle 22 with a valve 23 and is actuated by a compression spring 24 which tends to displace the slide and the valve so that the latter bears against a seat 25 formed in the channel 16. At its free or outer end, the valve spindle 22 is provided with a stop 26, such as a disc, which, when the valve 23 rests against the seat 25, may be actuated by a lever 27 for withdrawing the valve from the seat 25. The slide 21 is acted upon by the spring 24, and also by the liquid pressure in the channels 16, 17. In the channel 17 is a valve or slide 28 which is biased by a spring 29, the compression of which can be adjusted by means of a screw 30. The valve 28 is actuated by the liquid pressure in the channel 17 against the action of spring 29.

In a centrifugal separator as described above, the rate of discharge through line 3 may be regulated by means of the valve 4 without any risk of over-flowing of the bowl. At normal output of the separator, the slide 21 and valve 23, which form a movable shut-off device, take approximately the mean position shown in FIG. 3, where the pressure from the liquid in the discharge passage 17 acting upon the slide 21 is balanced by the pressure of the spring 24 and the liquid pressure in the passage 16. In this connection, the pressure of the spring 29 acting upon the slide 28 must, of course, be so adjusted in relation to the liquid pressure in the passage 17 of discharge line 3 that this slide does not close the line 3. If the discharge line 3 is now throttled by means of the valve 4, it causes a pressure increase in the line 3, whereby the slide or valve 21 is displaced to the left to one of its extreme positions, so that the communication channel 20 between the feed and discharge lines 2-3 is opened. At the same time, the slide 21 closes the channel 16 so that the feed supply to the separator is interrupted. Thus, to the extent that the bowl discharge cannot pass through valve 4, it is recycled to the bowl by way of return line 20 and pipes 18 and 2a.

If, on the other hand, the liquid level in the separator bowl for some reason should be displaced outside the pe- 3 riphery of the paring disc 7, which may happen if the liquid seal in the separator bowl is destroyed, this would normally mean that all separation material supplied to the separator bowl would discharge through the outlet 12 and thereby be lost. Such a mishap is avoided by the present invention, because the pressure in the channel 17 in that case will decrease so much that the slide 21 is urged to its opposite extreme position in which the valve 23 rests against the seat 25 and thus cuts off the supply of the separation material, while the return line 2% remains closed by slide 21. In this case, the non-return valve 28 comes into operation and closes the discharge line 3 so that the liquid therein does not rush back to the paring disc 7 and into the separator. After the liquid seal in the separator has been restored, as by supplying the required quantity of liquid in the usual manner, the separation may be resumed by loosening the valve 23 from the seat 25 by means of the lever 27 and the stop 26.

For operation of the device in the manner described, it is of course not necessary that the compression of the spring 29 be adjustable by means of the screw 3%, if the separation is carried out under constant running conditions. However, by arranging the spring 29 so that it can be adjusted, it is possible to utilize this adjustment to counteract changes in the operating conditions and also to effect displacement, in a centrifugal separator of the purifier type, of the boundary surface between the two separation components to the best position in the separator bowl. That is, by increasing the compression of spring 29, the liquid pressure in the bowl outlet may be increased and thus the position of this boundary surface may be changed. The boundary surface may thus be displaced so iar that the liquid seal in the separator bowl is destroyed, both the separation components then discharging through the outlet 12 for the heavier component. This causes the shut-off device to come into operation, in that the pressure in the channel 17 falls oii so that the valve 23 is moved so as to bear against the seat 25. By then adjusting the compression of spring 29 to a value which is somewhat lower than that value at which the two components discharge through the outlet 12 for the heavier component, and by resuming the separation, it will thus be possible to adjust the separator to the most suitable running conditions.

The regulating device may be made as an independent unit. However, as indicated in FIG. 3, it may alternatively be built into the shaft around which the usual frame cover (covering the separator bowl) is arranged to swing. For this purpose, the shaft is tubular and has two parts 31, 32 which are supported by brackets 33, 34 projecting from the lower part of the separator frame. The intermediate part 35 may be a part of the frame cover, and those parts of the feed and discharge lines which are between the regulating device 5 and the separator bowl 6 may consist of channels arranged in this cover. The intermediate part 35, as shown, is pivotally mounted on the parts 31 and 32 and is sealed against them by means of sealing rings 36, 37. The parts 31, 32, 35 thus form a housing of the regulating device 5.

Other types of centrifugal separators than that shown in the drawing may be provided with a regulating device according to the invention. The centrifuge bowl proper, an embodiment of which is shown only schematically in FIG. 2, should, of course, be formed by an upper and a lower part held together with a locking ring or in any other suitable manner, as is well known in the art. The centrifuge bowl may, if desired, be provided with nozzle openings and be arranged for automatic, intermittent, or continuous sludge discharge. Instead of the paring disc 7, the centrifuge outlet may be provided with a pump, such as a centrifugal pump, by means of which the separated lighter liquid component is fed to the discharge line 3 from the centrifugal bowl.

I claim:

1. In a centrifugal separator having a centrifugal bowl,

a feed line leading to the bowl for delivering thereto a feed material to be separated, and a discharge line leading from the bowl for discharging a separated component of the material, the combination of a return line connecting said feed line and said discharge line, a movable shutoff device in the return line, said shut-off device having a first extreme position for closing said feed line while the return line is open, an opposite extreme position for closing both the feed line and the return line, and an intermediate normal position for closing said return line while the feed line is open, and means for moving the shut-off device in response to variations in the diiference between the pressures in said feed and discharge lines, said pressure-responsive means being operable to move the shut-off device to its first extreme position in response to an increase in the discharge line pressure relative to the feed line pressure and to move the shut-off device to said opposite extreme position in response to a decrease in the discharge line pressure relative to the feed line pressure.

2. The combination according to claim 1, in which the shut-01f device includes a slide, said moving means including a housing containing the slide and having passages through which the pressures in said feed line and said discharge line are operable on the slide in opposing directions, respectively.

3. The combination according to claim 1, in which the shut-oif device includes a slide, said moving means including a housing containing the slide and having passages through which the pressures in said feed line and said discharge line are operable on the slide in opposing directions, respectively, said moving means also including a biasing element urging the slide in one of said directions.

4. The combination according to claim 1, in which the shut-off device includes a slide, said moving means including a housing containing the slide and having a passage through which the pressure in the feed line is operable on the slide to urge it toward said opposite extreme position, the housing also having a passage through which the pressure in the discharge line is operable on the slide to urge it toward said first extreme position.

5. The combination according to claim 1, in which the shut-off device includes a slide, said moving means including a housing containing the slide and having a passage through which the pressure in the feed line is operable on the slide to urge it toward said opposite extreme position, the housing also having a passage through which the pressure in the discharge line is operable on the slide to urge it toward said first extreme position, and a spring urging the slide toward said opposite extreme position.

6. The combination according to claim 1, in which the shut-ofi device includes a slide, said moving means including a housing containing the slide and having a passage through which the pressure in the feed line is operable on the slide to urge it toward said opposite extreme position, the housing also having a passage through which the pressure in the discharge line is operable on the slide to urge it toward said first extreme position, and a spring urging the slide toward said opposite extreme position, the spring exerting a pressure on the slide which, in the intermediate position of the slide, is equal to the diiference between the opposing pressures exerted on the slide through said passages.

7. The combination according to claim 4, comprising also a stationary frame supporting said housing, the housing forming a cover-supporting shaft and containing said return line and part of each of said feed and discharge lines.

8. The combination according to claim 1, comprising also a non-return valve located in said discharge line beyond the return line, reckoned in the flow direction through the discharge line, said valve being operable to close the discharge line in response to a predetermined low pressure in said discharge line.

9. The combination according to claim 1, comprising also a non-return valve located in said discharge line beyond the return line, reckoned in the flow direction through the discharge line, said valve being operable to close the discharge line in response to a predetermined low pressure in said discharge line, and an adjustable spring biasing said valve in a direction to close said discharge line.

References Cited in the file of this patent UNITED STATES PATENTS Ruda Jan. 17, 1939 Trautman July 20, 1948 Cahill Feb. 7, 1950 Jensen May 30, 1950 Jay June 5, 1956 

